1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to updating a license and providing content using the license, in order to protect a copyright of digital content.
2. Description of the Related Art
As content becomes digitized, a digital rights management (DRM) technique for protecting a copyright of digital content is necessary. Copyrighters want to protect their copyrights, while users want to use contents conveniently. In order to satisfy such requirements, various DRM techniques have been developed. In order to protect copyrights when using content under various scenarios, studies into methods of establishing rules regarding content use with a license file that is separate from the content and controls content use, as well as DRM concerning simple encryption, are actively underway.
A representative DRM method is “MS-DRM” developed by Microsoft Corporation.
Details regarding content use can be controlled by means of a license. For example, a license can control content to only be played, allow copying of content, control the use term and amount of content use, control content conversion, etc. As such, a license can be made out to reflect various business models or various user scenarios in terms of the content use. By controlling content to be used only in a manner defined by the corresponding license, a copyright for the content is protected.
Generally, a license includes an electronic signature for determining whether the license has changed or has been hacked, as well as containing basic information for indicating the corresponding content and identifying the license. Also, the license includes information regarding a rule for controlling content use. In order to describe rule for content use, a standardized language, etc., such as XML-based “XrML”, adopted as a standard in the MPEG Right Express Language (REL) is used. In order to include various user scenarios, new techniques are being established. Also, the license further includes information for generating a decryption key for decrypting the corresponding encrypted content. The decryption key information is combined with unique information of a device which tries to use the content and then is used to generate a key for decrypting the content.
Accordingly, in order to utilize content protected by DRM, as illustrated in FIG. 1, a user 1 receives desired content together with a license for the content from a provider 2, and uses the content only in a manner defined by the license. If the content has a use term from Jan. 1, 2006 to Jan. 10, 2006 and is allowed for playing only, the user 1 can play the content only during that period. If the user 1 wants to use the content after this period elapses, the user 1 must receive a new license for the content from the provider 2. In some cases, the user 1 must again download the corresponding content together with the new license.
Generally, since a license is a minimum of 128 bytes, it is very difficult to download the license when the corresponding apparatus or device is disconnected from a network. Particularly, in order to update a license through a mobile device, etc., a personal computer (PC) is needed. A convenient method is to download an updated license through a telephone or a mobile phone which can be connected to a network from wherever the user is. However, it is difficult to retransmit a license downloaded from the telephone or a mobile phone to a device which tries to use the corresponding content. Furthermore, it is difficult to transmit a license through short message service (SMS), etc. of a mobile phone, due to the large size of the license. Accordingly, a new method for solving the above-mentioned problems is needed.